Air Admittance Valve for branch line vent?

[acacali]

Here is my situation: we very recently moved into a new house and discovered that the kitchen sink, which is on a separate branch than the main waste stack and vent, is venting directly into the space between our first and second floors. The second floor is an addition, and the space between the floors is 30", so I was able to crawl in there to discover that the steel vent pipe coming from the kitchen is wide open and emitting sewer gas right into the home (it stinks). So, can I simply add an air admittance valve at the top of the vent pipe in the space between the floors - which would be much, much easier - or do I need to extend the pipe some distance away to the main vent stack and connect it there? Thanks.

 

[phishfood]

The BEST option, and the one that I would pursue if it were possible, is to reconnect it to the main vent. If that is not possible, or would cause lots of drywall removal and repair, an air admittance valve is acceptable, as long as it is accessible by means of an access panel or the like.

 

[johnjh2o]

The preferred way would be to connect it to a existing vent or through the roof. If the waste line isn't connected to the main waste line a AAV may not work. AAV's will allow air to enter the line but will not allow back pressure to escape.

 

[acacali]

The kitchen waste line is connected to the main waste line, it's the kitchen vent line that's connected to...nothing. If I would connect it to the main vent stack, it would be 12 feet or so away, connecting to the vertical vent line of the shower in a neighboring second floor bathroom. Does that sound acceptable? (I know, hard to tell without seeing it.)

 

[johnjh2o]

If your connecting to another vent you must connect 6" above the flood rim of the highest fixture the vent is serving. In most cases that would be 42" above the floor.

 

[acacali]

Thanks John. That helps. I may need to rethink where to attach it, unfortunately. The plumbing in the bathroom is mostly exposed (the bathroom is partially gutted at this point) but there are a lot of connections in a tight space, so it won't be easy. That's why I would prefer to put in the air admittance valve, but it sounds risky.